In the electronics industry, as products such as cell phones, game controllers, personal video players, and camcorders become smaller and smaller, increased miniaturization of integrated circuit (IC) packages has become more and more critical. At the same time, higher performance and lower cost have become essential for new products.
Usually, many individual integrated circuit devices are constructed on the same wafer and groups of integrated circuit devices are separated into individual integrated circuit die. An integrated circuit package may hold multiple of the same type of die or it may be mixed with die from a completely different technology.
In order to interface an integrated circuit die with other circuitry, it is common to mount it on a leadframe or on a multi-chip module substrate that is surrounded by a number of lead fingers. Each die has bonding pads that are then individually connected in a wire bonding operation to the lead fingers of the leadframe using extremely fine gold (Au) or aluminum (Al) wires. The assemblies are then packaged by individually encapsulating them in molded plastic, epoxy, or ceramic bodies.
One approach to putting more integrated circuit dies in a single package involves stacking the dies with space between the dies for wire bonding. The space is achieved by means of a thick layer of organic adhesive or in combination with inorganic spacers of material such as silicon (Si), ceramic, or metal. Unfortunately, the stacking adversely affects the performance of the package because of decreased thermal performance due to the inability to remove heat through the organic adhesive and/or inorganic spacers. As the number of dies in the stack increases, thermal resistance increases at a faster rate. Further, such stacked dies have a high manufacturing cost.
Another approach is to put more integrated circuit dies side-by-side in a single package but this results in packages taking up large areas on the printed circuit boards. As consumer electronic devices are constantly shrinking, adding to the size of the printed circuit board is unacceptable.
Each attempt to reduce the size of the integrated circuit package tends to create additional problems with cost, heat transfer, and electrical performance. Thus, a need still remains for an integrated circuit packaging system with stacked die to simplify the assembly process while preserving thermal characteristics of the finished package. In view of the industry demand for higher density and smaller integrated circuit packages, it is increasingly critical that answers be found to these problems. In view of the ever-increasing commercial competitive pressures, along with growing consumer expectations and the diminishing opportunities for meaningful product differentiation in the marketplace, it is critical that answers be found for these problems. Additionally, the need to reduce costs, improve efficiencies and performance, and meet competitive pressures adds an even greater urgency to the critical necessity for finding answers to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.